This invention relates to a ladder base stabiliser device and in particular it relates to a device which can be attached to or form part of a foot assembly of a ladder which can be used to prevent ladders from moving or slipping whilst is service, allowing ladders to be safely used on non level ground.
The use of ladders, particularly on uneven or sloping ground can give rise to safety problems, for example arising from ladder movement with the top of the ladder moving sideways, or from base slip when the bottom of the ladder moves away from the wall on which the top of the ladder is resting.
It is known that by widening the base of a ladder the ladder is made more stable reducing the tendency for sideways movement of the top of the ladder and there have been many patent applications made for inventions which try to overcome these and similar problems.
There are a number of ladder base stabilisers on the market that are either xe2x80x98clip onxe2x80x99 or xe2x80x98bolt onxe2x80x99 devices and which are designed to ensure greater safety in the use of ladders. These generally work well on solid level surfaces, but are far less effective on uneven, or sloping ground.
A known ladder stabiliser provides suitably restrained struts to the ground from points on the stiles a distance up from the base, with these struts leaning in the opposite direction to the ladder and outwards from the line of the stiles, forming a pyramid shape at the base. The ladder is both prevented from toppling sideways and the base is prevented from moving away from the wall on which the top of the ladder is resting.
This device can prove awkward in use and the difficult to store away.
I have devised an improved ladder base stabilising device allowing a ladder to be safely used whatever the slope of the ground and which is easier to use in practise.
The present invention overcomes the difficulties of stabilising ladders when founded on uneven, or sloping ground. It can be permanently fixed to the ladder and has minimum projection from the side of the ladder stile when not in use allowing easy ladder transport and storage. It is easy to operate and position allowing the job of making a ladder safe very quick and therefore far less likely to be overlooked. Being permanently secured to the ladder the device won""t get lost or mislaid and with no loose components it is always ready for use.
The device of the present invention can be sold separately from a ladder and attached to a ladder or ladders can incorporate the device.
The device of the present invention can be used in conjunction with the ladder levelling device as described in Patent Application PCT/GB98/03465 in which there is disclosed a device that can accommodate uneven ground by adjusting the effective length of the ladder stiles and can also be used with a range of ladders.
According to the invention there is provided a ladder stabiliser device which comprises two telescopic arms or struts mounted on the outside of the ladder stiles at a distance up from the base of the ladder, the telescopic arms or struts being adapted so that, when the ladder is resting against a supporting wall, they are able to positioned so they are sloping outwards from the stiles and rearwards towards the wall or surface on which the top of the ladder is resting, the telescopic arms or struts being attached to the ladder through a double spring loaded device that enables there to be compound rotary motion of the telescopic arms or struts while at the same time forcing them to maintain a predetermined angular rotation in respect the ladder stile, both outwards and rearwards directions from the base of the ladder.
Preferably when not required the arms or struts can be manually rotated against the force of the springs so that the arms fold flat along the line of the ladder stiles. Preferably there is a simple clip which can oppose the double spring forces so that it will then hold the arms in the inoperative position against the style allowing easy storage and transport.
There can be ties which, in use, can link the struts together and also link them individually to the base of the ladder stiles.
The double spring loaded device removes the need to provide rigid ties between the base of the struts and the bottom of the ladder stiles in order to achieve correct angular positioning of the struts in relation to the ladder and, preferably the ties are non rigid e.g. made of a flexible rope, cord, chain etc.
Preferably the ties are made of a hard wearing material such as xe2x80x9cNylonxe2x80x9d or similar straps that will withstand the rigours of use better than solid ties and do not suffer the disadvantage of solid ties which are very vulnerable to damage due to bending should anyone stand on them by mistake.
Preferably on the lower end of each telescopic arm or strut is mounted a foot component that allows movement in two directions, maintaining the adequate transfer of loads to the ground whatever the slope of the surface, e.g. with up to 10 degrees of crossfall being accommodated by movement of the foot component.
Preferably the main longitudinal components of the device will be constructed of extruded and hollow box sections. The design of the extruded sections allow the incorporation of end fixings generally without special machining operations.
In use to achieve the desired orientation from the storage to operating positions of the struts in relation to the ladder stiles requires two components of movement,
1. Rotation in line with the stiles and perpendicular to the line of the treads allowing the struts"" feet to be located nearer to the wall or vertical surface on which the top of the ladder is resting than the base of the ladder.
2. A swing motion to extend the lower ends of the struts sideways, out from the ladder extending the width of the ladder base.
When used as stabilisers for access towers and the like the device only requires the second component, namely swing away from the perpendicular, as the uprights or posts on a tower, unlike a ladder stile, remain vertical.
In order to achieve these two components of movement while still effectively transmitting loads from the ladder through the strut to the ground there is preferably provided a hub and spring arrangement that allows these two components of movement to be achieved.
Preferably the unit is designed so that handed versions can be produced for each side of the ladder using identical internal components assembled the opposite way round so reducing the initial tooling costs.
The hub and spring unit preferably comprises a first component bolted to the ladder which consists of a chamber holding a spiral spring with one end of the spring being fixed in position in the chamber, the second component fits rotatably over the first component to form the other half of the spring chamber and is attached to a strut, the second component is attached to the other end of the spring so that relative rotation of the two components tensions the spring.
The unit is preferably made using injection moulded engineering grade plastics for the basic shells, alternative materials such as cast metal could be used.
The struts can be of any length for example a strut length of around a meter is suitable however there is no reason why the length should not be longer, providing greater stabilising capacity while utilising the same hub design and tie arrangement.
The preferred hub design, although it has end stops within the unit to limit further movement beyond the operating positions, preferably does not take cantilever forces, relying on the strap ties to provide the lateral restraint to the ends of struts.
With shorter strut lengths e.g. of or around half a meter, the hub design can be made stronger to provide greater resistance to limit further movement at the operating positions, thereby providing cantilever capability within the hub. This would allow the device to be used without physical ties or straps.
At the bottom of the struts a device as described in Patent Application PCT/GB98/03465 could be incorporated allowing easier final adjustment of the stabiliser. With the short version as above this would provide the only adjustment necessary. With the medium and longer versions, while making final adjustment easier, cheaper options could rely on simple tensioning of the ties.
In use, an embodiment of the invention uses a hub design which comprises a fixed injection moulded component securely bolted to the ladder stile, with a long bolt passing through a hollow rung which pulls together the first component of a pair of hub units on both sides of the ladder and attaches them to the ladder and projecting pins moulded as part of the back face of the unit provide load transfer to the stile, while allowing some to be easily broken off to accommodate the rung projection.
To assemble the chamber the spiral spring is held within the chamber by means of projecting lugs with an inner lug attaching one end of the spring to the chamber while the outer lug only temporally holds the other end of the spring until the second component is inserted and the spring tensioned.
Preferably on either side of the outer lug are two further smaller projections each with a ramp section nearest to the outer lug The spiral spring can be loosely wound and positioned within the unit in either direction, allowing the completed unit to be handed.
The outer or rotating moulded component holds the attachment to the struts and forms the other half of the circular spring chamber. When inserted into the fixed part, arms within the chamber pick up the end of the loosely coiled spring. Rotating the component then tensions the spring, with the ramps section correctly locating the spring. When fully tensioned the long bolt is fully tightened pulling the unit together so that projections lie within recess to limit overall rotation of the device in service.
Preferably the strut attachment arms include a spring-loaded roller device that acts on a sloping ramp so that the arms are caused to rotate outwards from the stile of the ladder.
The device is suitable for use with longer strut versions with ties at the lower ends of the struts. Where additional strength is required to limit rotation both rearwards and outwards for shorter cantilevered strut version with no end ties, a similar design would be used but with greater strength to take the forces involved.
The struts can be extended and, generally, the simplest way of providing a locking facility between two telescopic tubular components without loose bolts etc. is to have an internal spring with one or two projecting lugs attached that pass through the inner tube and engage into a series of holes in the outer tube.
Depressing the lug allows the outer tube to be moved until the lug springs out again through the next hole or, if the outer tube is rotated, the lug will miss the adjacent holes until the alignment is restored, a difficult and awkward operation even when there are guide marks to help. With square or rectangular tubes this rotation is not possible so this simple spring and lug device is not suitable when the telescopic movement required is more than just one or two holes. Another problem with this simple internal spring device is that it is very difficult to provide positive locking to prevent the lugs from being accidentally dislodged when under load due to excessive wear and elongation to the holes through the tubes, especially the inner, and they are also difficult to inspect without dismantling.
To overcome the above problems while still allowing large telescopic expansion and small incremental adjustment and the use of square or rectangular tubes I have devised a new development of the simple spring and attached lug arrangement and the invention also provides an improved device for locking together the two parts of the telescopic arms or struts, so that the overall length of the arms can be varied easily and quickly without any loose bolts etc. or awkward spring loaded pins.
The two telescopic tubes are locked together at the desired location by small metallic lugs attached to a pair of flat springs secured to the external surface of the outer tube. The lugs pass through a pair of holes in the outer tube and mate with a series of holes through the wall of the inner tube.
The depth of penetration of the lugs through into the inner tube is controlled by sloping wings formed as part of the springs projecting each side of the lug. To extract the lug these wings slide up inclined ramps, and to lock the lug in the fully inserted position, cams cover the wings preventing movement. In addition the wings have small reverse slopes on the leading edges that prevent the cams from fouling the wings during certain movements.
The operation of the telescopic arms is controlled by an injection moulded handle that completely surrounds the outer telescopic tube. The handle has a push button which, when depressed, allows the handle to move freely along the tube for a limited distance to be restrained by a pair of blocks within the handle fixed to the outer wall. In one embodiment the blocks also form the attachment of the springs to the outer tube as they have protecting pins moulded into the block that pass through the spring and into the wall of the tube, being totally contained within the moulded handle, there is no need to provide further fixing of the blocks or springs. When the push buttons are released the handle""s position along the tube is further restrained in one of three possible positions, allowing the following:
Extractedxe2x80x94Lugs are pulled out from the inner tube and maintained in that position allowing totally free telescopic movement.
Free to Movexe2x80x94Lugs are free to move either in or out of the inner tube under the power of the spring that will push the lug through the next available hole in the inner tube when this is moved in or out, thus locking the tubes in that selected position.
Safety Lockedxe2x80x94Lugs are fully inserted through both tubes and are physically restrained in that position.
The push button is supported by a moulded arm formed integral with the casing and operates a cam through a moulded lever and double hinge arrangement. This cam acts on the fixed blocks, to control and limit the movement of the handle to achieve the above three variations of position.
Using this device, adjustment can even be achieved with the user wearing thick gloves etc.